The present invention relates to a metal gasket which can prevent mis-assembly or wrong assembly of a metal gasket formed by laminating three or more sheets of metal plates, held between two members for sealing; and a mis-assembly detection method of a metal gasket which only requires a simple device and can be easily automatically made.
For an automobile engine, metal gaskets such as a gasket sealing a simple sealing-target hole at an intake manifold or exhaust manifold and so on, or a cylinder head gasket sealing between a cylinder head and a cylinder block, are used. The above-mentioned metal gaskets are manufactured by laminating multiple metal plates with different materials, thicknesses, or processes, and in order to obtain a desired sealing capability, these multiple metal plates are required to be laminated in a correct direction on a correct side in a correct order.
However, in many cases, the shapes of the metal plates have roughly the same configuration, so that it is difficult to determine the direction, front or back sides, or the assembly sequence of the lamination of the metal plates. In such a case, when the metal plates are laminated, the direction, front and back sides, and assembly sequence of the lamination may be easily mistaken.
In order to solve the above-mentioned problem, proposals were made for mis-assembly discriminatory structure of a metal laminate gasket wherein at least a part of one surface of each structural plate is placed in order in a staircase pattern and exposed to the outside, or wherein at least a part of one surface of each structural plate is exposed to the outside so as not to overlap with one another during assembly (for example, refer to Japanese Utility Model Publication (JIKKAI) No. S62-114270 and Japanese Patent Publication (TOKKAI) No. S62-159866), so that the assembly sequence, that is, the number of the assembly order of each single structural plate of the laminated metal gasket can be clearly recognized.
Also, a cylinder head laminate gasket was proposed wherein at least one sheet of matching plate overlaps a sheet material; a mark showing the thickness of the sheet material is provided in a position displaced to one side from the center of a bore of the sheet material; and a notch is provided in a position corresponding to the mark in the matching plate. Also, a laminate metal gasket was proposed, wherein each metal plate forming the gasket includes a notch, engraved mark, marking and the like for recognizing the number of the assembly sequence of each metal plate. (For example, refer to Japanese Utility Model Publications (JIKKAI.) No. H1-165857 and No. H6-85963)
However, even with the structure which is visually recognizable as mentioned above, the gasket is assembled by determining a projection or groove of the laminated gasket, so that an irregularity of a minute part of the laminate plate with a similar color has to be recognized. Accordingly, human error cannot be completely prevented when the projection or groove is determined. Moreover, a device for preventing mis-assembly is required.
The invention is made in order to solve the problems described above, and an object of the present invention is to provide a metal gasket which is formed by laminating multiple metal plates, and can be easily recognized by an assembler or observer when the assembly sequence of the lamination of the metal plates is incorrect.
A further object of the present invention is to provide a mis-assembly detection method of the metal gasket which requires only a simple device and can be easily automated.
Further objects and advantages of the invention will be apparent from the following description of the invention.